In the late 1930s, the democracies failed to understand how totalitarian aggression combined diplomacy, propaganda and military force. We understood Germany's just complaints and did not care about technical military factors. As a result many people died.

There are two processes at work in Central America and the Caribbean today. One process is the struggle against poverty and toward greater freedom and justice. This is primarily a heart-rending cultural learning experience in each country. It is slowed by disagreement about goals and means, excess selfishness and other human weaknesses. Mistakes and serious setbacks seem to be inevitable, and they produce much suffering.

This first process has produced much progress in the last 20 years. Politically, a complicated accounting would show a net gain for democratic values. Economically, progress has increased life expectancy by more than 10 years, and average real income by half. We should help more--and more wisely--than we have, so this process would go a little faster.

The other process is a series of efforts to expand the area of left-wing totalitarian, anti-U.S. control. Cuba plays the leading role in this process because of Castro's skills and prominence, the strength of Cuba's army and the capabilities of Cuba's intelligence service, the DGI. The Soviet Union is influential with Cuba, providing 25 percent of its GNP, $3 billion per year, and controlling Cuba's secret service since an agreement made in 1968, with many Russians working full-time at the DGI headquarters in Havana. Other Communist governments from outside the region, various Palestinian terrorist groups and others often work with Cuba and its local allies. Of course, each country and group makes its own decisions. Internal differences are a potential source of weakness, as in any coalition or organization.

Despite substantial gains in the first process, the second process has become much more dangerous in the last five years, and there is a good chance that it will make additional gains in the next few years, producing much suffering and loss of freedom, and even U.S. security problems.

The principal current arenas are Nicaragua and El Salvador. In Nicaragua, after a broad international coalition of democratic and Communist countries and local groups had combined to end the Somoza dictatorship in 1979, the Marxist-Leninist Sandinista Directorate, which had led the coalition against Somoza, began an unreported political war against the democratic elements of that coalition. Thousands of people were sent to Nicaragua by Communist countries to help the Sandinistas. But the democracies gave virtually no help to the democratic Nicaraguans in their effort to defend themselves. There was almost no outside response when the Sandinistas renounced their written promise to the Organization of American States to hold elections promptly. The Sandinistas have almost won their subtle war against their former partners.

Also in Nicaragua the government has been working intensively for about 18 months to build a modern 50,000-man army and air force. If this buildup is successfully completed as expected in the coming months, the Nicaraguan army will be overwhelmingly the most powerful military force between Colombia and Mexico, and could be used subtly or directly to support totalitarian aggression with its various claims of justice.

In El Salvador a democratic army officer corps deposed the old army-landlord alliance in October 1979 and threw out more than two- thirds of the officers above the rank of major. In 1980 it brought in the main democratic left-wing opposition party, the Christian Democrats under Napoleon Duarte, to prepare for elections in March 1982 and to implement land reform, nationalize the banks and the coffee and sugar export businesses, improve the school system, etc. The revolutionary army also removed the leadership of the feared Salvadoran security forces and started the process of cleaning up these organizations, a task it has largely, but by no means completely, accomplished.

After the revolution in El Salvador, Castro succeeded in getting the four small armed groups that had been fighting the government there to form the FMLN, which now has a force of several thousand guerrillas fighting to throw out El Salvador's revolutionary government and prevent elections. The FMLN is mostly Salvadoran rural teen-agers, but most of its leaders and specialists have received foreign training, and, of course, their military supplies come mostly from and through Communist-controlled countries (and Cuba's recent ally, Mexico).

Despite the FMLN's lack of substantial popular support, either side could win militarily in El Salvador. Large changes in the military capabilities on both sides could happen quickly. The situation is very dynamic and strongly influenced by technical details. The outcome is unpredictable.

If El Salvador's revolutionary government falls, there seems to be little possibility of preventing either the repressive military regime in Guatemala or the freely elected civilian government of Honduras from being replaced by Marxist-Leninist regimes allied to Cuba. Then drastic polarization is likely to be started in Mexico, which is nominally revolutionary but socially backward. The outcome of violent conflict in Mexico is difficult to predict, but not likely to be without serious security implications for the United States.

While the democracies cannot stop this process as easily as they could have stopped Hitler in 1936 or 1937, they can effectively use political action to organize support for democratic groups in Nicaragua and for the revolutionary government in El Salvador, and take relatively small, but intelligent, military measures. Our great unused weapon is truth. Any action against remaining democratic forces in Nicaragua must be a worldwide political event. La Prensa, Bishop Ovando y Bravo, the free trade unions, the Social Democrats and others are potentially significant forces. They must be given all the resources they can use and a worldwide network of visible supporters. At home and abroad, Cuba also is vulnerable to truth.

If this time the democracies can achieve the political will and understanding to resist totalitarian aggression based on propaganda, diplomacy, terror and military force, then the necessary means can be found. Without the understanding and will, nothing can be done.